Plants to 3 cm tall, dull yellowish brown when dry, forming loose cushions. Stems frequently dichotomously branched. Leaves appressed when dry, curved outwards when wet, ovate-lanceolate, 2.8–3.7 mm long, 0.7–0.8 mm wide, canaliculate, keeled, plicate with 2 pleats on either side of the costa; apex concolorous; margin revolute in the basal 50–67%, single-layered throughout, entire; costa very short-excurrent. Upper lamina unistratose; laminal cells elongate, 25–50 × 8–10 μm, with nodulose walls; more distal cells shorter, isodiametric to oblong; basal cells longer, not nodulose; basal angles with thin-walled slightly inflated cells, extending a short distance along the margin in a single row. Perichaetia and sporogones not seen in Australian material.

Racomitrium ptychophyllum is slightly more robust than R. crispulum, but it is readily recognised by its doubly plicate leaves.

Native.

Grows on basalt at 1690–1760 m.

Grimmia ptychophylla Mitt., Trans. Bot. Soc. Edinburgh 8: 280 (1866); Racomitrium ptychophyllum (Mitt.) Mitt., Handb. New Zealand Fl. 2: 426 (1867). Type: Otago, New Zealand, W.L.Lindsay; holo: NY n.v.

Vic.: Ruined Castle, Bogong High Plains, K.Ralston [N.Klazenga] 5166 (MEL); Basalt Hill, at head of Rocky Valley, Bogong High Plains, J.H.Willis 58 (MEL).

Klazenga, N. (2012), Australian Mosses Online 62. Grimmiaceae. Australian Biological Resources Study, Canberra. Version 16 August 2012. http://www.anbg.gov.au/abrs/Mosses_online/62_Grimmiaceae.html